Translucent materials



Dec. 12, 1961 G. c. o. LODGE 3,012,477

TRANSLUCENT MATERIALS Filed May 2, 1957 3 Sheets-Sheet 1 FIGJ, Fl6.2. 16

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Attorheys Dec. 12, 1961 Filed May 2, 1957 G. c. o. LODGE 3,012,477

TRANSLUCENT MATERIALS 3 Sheets-Sheet 2 Inventor Attorney? G. C. O. LODGETRANSLUCENT MATERIALS Dec. 12, 1961 Filed May 2, 1957 5 Sheets-Sheet 3FIGQ.

Inventor 460% 54kg f/(Vyr lod e y Attprneyi United States Patent3,012,477 TRANSLUCENT MATERIALS George Clive Oliver Lodge, Ryde, Isle ofWight, England, assignor to Arthur Ash, Ryde, Isle of Wight,

England Filed May 2, 1957, Ser. No. 656,605 Claims priority, applicationGreat Britain May 4, 1956 4 Claims. (Cl. 8857.5)

This invention relates to translucent materials, especially those insheet form for use as cloches or for the glazing of greenhouses.Considering greenhouses and similar structures in their simplest form,light which falls on the translucent material of which the structure ismainly composed will, if the angle of incidence is large, penetrate thesheet material only in limited quantity, and large fractions of thelight will be reflected externally and the effect of such reflectedlight will be totally lost so far as the interior of the structure isconcerned. In the case of a greenhouse this is a very important factor,because during the early part of the day and in the eve ning the lightis low, i.e. the rays of the sun fall at a high angle of incidence; thiseffect is more pronounced during the spring and autumn. It is clearlyadvantageous that the maximum amount of light be transmitted into thegreenhouse, and that the minimum be reflected externally, and it is anobject of the present invention to provide a material which is not onlyeasily produced but will enable greater quantities of light thanheretofore to be transmitted and so trapped in such structures.

According to the invention a translucent sheet material is formed on onesurface thereof with convexities spaced apart by a distance at leastequal to the width of the convexities and on the other surface withconcavities in register with said convexities, the thickness of thematerial being approximately constant over its whole surface. 7

In a preferred form the convexities and concavities are hemispherical,but it will be appreciated that an improvement over known materials,though to a lesser degree, may be effected through other shapes such asprismatic or elliptical projections.

Preferably also the convexities are arranged in rows and are spacedapart, e.g. in the case of hemispherical convexities, at distances oftwo diameters, centre to centre. I

1 In anygiven sheet of material, one or more of the oonvexities may bearranged to be removable, normally being retained in a seating, butdetachable therefrom so as to, give access to the other side of thesheet so that the interior of the structure may be ventilated.

Alhough it is convenient .to have the thickness of the materialsubstantially constant, it may be desired to make the apex of aconvexitysomewhat thickerthan' the walls oflthe convexity, so as to forma lenticular portion at the apex;

The side of the sheet of material on which the concavities are formedmay have applied thereto a pressure.- sensitive adhesive, so that thematerial according to the invention may be applied to the outside of anexisting structure such as a greenhouse.

I In' some cases it may be desirable that at least one margin of some orall of the sheets according to the invention is formed with means forengaging with complementary means on another sheet. Such means may takethe form of pegs, teeth, or other shapes which will enable one sheet tobe readily fastened to another.

Embodiments of the invention will be described with reference to theaccompanying drawings, in which:

FIGURE 1 indicates diagrammatically the path of a ray of light fallingon a sheet of glass.

3,012,477 Patented Dec. 12, 1961 FIGURE 2 indicates diagrammatically thepaths of rays falling on material according to the invention,

FIGURES 3, 4 and 5 show, in diagrammatic plan, various alternativedispositions of hemispherical convexities,

FIGURE 6 is a diagrammatic fragmentary sectional elevation of a sheet ofmaterial, according to the invention,

FIGURE 7 is a similar View, in contradistinction thereto, of materialnot according to the invention,

FIGURE 8 is a diagrammatic section illustrating the paths of raysfalling at an angle of incidence of 0.

FIGURE 9 is a fragmentary sectional elevation of a removable convexity,

FIGURES l0 and ll are diagrammatic representations of shock wavesimpinging on surfaces,

FIGURE 12 is a fragmentary section of an alternative form ofhemispherical convexity, and

FIGURE 13 is a similar view of a pyramidal convexity.

Referring to FIGURE 1, 15 represents a sheet of glass as ordinarilyemployed for a cloche or a greenhouse. 16 represents a ray of lightfalling thereon at an angle of incidence of 60. A substantial proportionof the incident ray is reflected, as indicated at 17, and

is refracted and passes to the interior of the structure.

It is clear, therefore, that only the fraction represented by 18 can beusefully employed.

Referring now to FIGURE 2, the sheet material 19 is glass or a plasticsuch as polythene or polystyrene, and for purposes of comparison is ofthe same thickness as the glass 15. It is formed with a hemisphericalconvexity 20.

Consider now an incident ray 21, having an angle of incidence of 60relatively to the sheet 19. Since the ray 21 is radial, it impinges onthe surface of the convexity at an angle of local incidence of 0, andsubstantially all the light (about 98%) passes inside, as indicated at22.

Consider next a ray 23 parallel to the ray 21. This has an angle oflocal incidence of 20, and therefore a small fraction (about 5%)indicated at 24, is reflected outwards, while a larger fraction,indicated at 25, passes inwards.

It will be seen, therefore, that the convexity of FIG- URE 2 will trapconsiderable quantities of light that would, with the flat sheet ofFIGURE 1, be reflected and lost.

Referring also to FIGURE 3, a sheet 26 of material is moulded frompolythene, polystyrene or from glass or other suitable material. Thedegree of translucency will depend on the characteristics required ofthe finished In the case of greenhouses, which are today frequentlyshattered by supersonic bangs from high-speed aircraft, it may bedesirable to employ a relatively resilient material such as polythene,rather than glass.

In the embodiment made from polythene, which may be readily moulded andcheaply produced, the sheet is made of a convenient size, say 2 ft. x 4ft., although, of course, the size may be related to the type of glazingeventually required. In shape, the sheet is rectangular and of asuitable thickness, say one eighth of an inch, as indicated in FIGURE 2.The sheet 26 is formed'with hemispherical 'convexities 20 On one side,and with corresponding hemispherical concavities (indicated at 27 inFIGURE 2) on the other side, the thickness of the sheet beingsubstantially constant over its entire surface. The diameter of each ofthe conve'xities 20 is, say, 1', and the convexities are arranged instraight rows in staggered formation, each convexity being spaced at adistance of two diameters from its immediate neighbours in its own rowand adjacent rows, being similarly spaced.

This spacing is of considerable importance. If the convexities were tooclosely spaced, each convexity would shield its neighbours to someextent from the impinging light, but if the convexities are spaced asdmcribed above, very little shielding will take place.

This is clearly shown in FIGURE 6. Convexities 20, spaced at twodiameters from centre to centre, have rays 28 falling on them at anangle of incidence of 75 It will thus be seen that rays having angles ofincidence up to 75 (the greatest angle normally encountered) can impingeon the convexities, the full surface of which can be utilised. If theconvexities were too close together, as is shown in FIGURE 7, the rays28 would impinge only on the upper parts of the convexities. Inconsequence, their angles of local incidence would be large, and aconsiderable fraction would be re flected and lost. Indeed, the lowerparts of the convexities, for example those parts below the line AB,would'be largely ineifective, and the benefits of the invention would belost.

Incident light falling normally, that is, at an angle of incidence ofwill penetrate the material with relatively little loss, there beingonly a small fraction of the light reflected externally.

This is illustrated in FIGURE 8. A ray 29 falling normally and radiallywill pass in with a loss of only 2%. A ray 30, also falling normally,but nearer the margin of the convexity, will be partly reflected, asindicated at 31, but mainly refracted, as indicated at 32. This,incidentally, shOWs that a desirable diffusion is effected within thegreenhouse.

When, however, the light falls'on the sheet at an angle of incidence ofabout 45 or more, much of it will fall on the hemispherical convexitiesat smaller angles of incidence in such a way as to pass through theconvexityv (see FIGURE 6), the local angle of incidence remaining at ornear 90, whereas, had the sheet been a continuous flat sheet, the angleof incidence would have been most of the light would the invention,instead of being reflected externally and therefore being wasted aswould occur with oridinary sheets of glass.

Thus, sheets according greater amount of the, light falling onto agreenhouse to be Further, the transmitted light is more diffused;

to the invention enable a transmitted thereinto to serve a usefulpurpose.

interfere with the formation of the convexities over the main area ofthe sheet.

Oonvexities may be of differing sizes in the same sheet if desired, andmay be arranged in patterns instead of in rows.

It is within the scope of the invention to provide a sheet of materialwhich may be affixed to the glass of an existing greenhouse. For thispurpose, as shown in FIGURE 6, a sheet 26 having convexities 20 may haveon the under side thereof a layer 36 of adhesive, preferably apressure-sensitive adhesivewhereby the sheet is merely pressed intoposition.

It is though that the superior resistance of the material to supersonicbangs is due not only to the resilience of, e.g. polythene, but also tothe shock-breaking and absorbent effect of the convexities on theimpinging air, and to the increased structural resistance imparted bythe convexities. I

FIGURES 10 and 1 1 illustrate this. In FIGURE 10 a fiat sheet of glass37 is subjected to a shock wave insimultaneous over the whole area ofthe sheet, so inducing vibrations in the glass sufiicient to break it.

In FIGURE 11, the wave 38' first hits the convexities 39, and by thetime it reaches the sheet 40 it has become disturbed, and so no longerhas an unbroken front which can produce the impact previouslyexperienced.

As the shock wave first impinges on the small areas of the tops of thedomes, pressure is transmitted through the walls of the domes, and thesheet 40' is prepared. gradually to receive the impact and to yieldthereto. Turbulence and counterwaves occur, with opposite and variousdirections of force, and much of the: energy of the shock wave is thusdissipated.

In the specification, it has been stated that the thickness of thematerial is approximately constant 'over its whole surface. There will,of course, be minor variations by reason of the provision ofconvexities, for example, at the junction of a convexity with the sheetthere may be quite an appreciable extra thickness but it is intended ingeneral that the thickness of a hemispherical convexity is, measuredradially, approximately the same as the thickness of the sheet, and thatsimilar considerations should apply for other shapes of convexity.

It is, however, possible to vary the thickness of the convexity, asillustrated in FIGURE 12, for example,

FIGURE .4 illustrates an alternative embodiment in which the convexitiesare arranged in rows in rectilinear.

fashion, while FIGURE 5 shows a more widely spaced arrangement instaggered formation.

The ventilation of a single cloche differs from that required for alarge greenhouse, but it can be arranged to any extent required bysimple means such as the provision of one or more removable convexitiesin one or more of the sheets making up a structure. simplest form, theventilating means could consist of a sheet having an aperture in placeof a convexity, the

.margin of the aperture being formed as a seating to accommodate aconvexity separately moulded so as to be capable of'location in theaperture during normal use.

In its,

A removable convexity is shown in FIGURE 9. The

.convexity 33 is'rebated as at 34' and is arranged. to seat removably inan aperture 35 in the sheet 26. Ventilation would then be promotedmerely by removing the convexity 33 from its seating. It could, however,be

' be moulded in a single sheet. Alternatively again, where to achievecertain elfects. Thus in FIGURE 12 the sheet 41 has a hemisphericalconvexity 42'formed with athickened apex 43 constitutinga lens. Thus, asheet ofmaterial can be designed to effect concentration of lightfalling overa predetermincdrange of angles. of incidence.

'There may be other forms of convexities For example,FIGURE13fillustrates a pyramidal convexity in or round-topped cone's.

When the material is to be used for cloches, it may be moulded in curvedor angled formation if desired. Thus, there may be a semi-cylindricalsheet, arranged to be located on the top edges of two fiat sheets whichare maintained in parallel and almost vertical relation, or

a sheet '45. Other shapes may be ellipsoids, trapezoids two flat sheetsmay be moulded in one at an angle of,

say, 45. Suchan angled sheetwould form a complete cloche. Alternatively,theDutch barn type of cloche may a flexiblematerial such 'azpolythene isemployed, the sheet may be moulded, with a weak band of reducedthickness, enablinglthe sheet to be hinged. This not only allows it tobe bent to any desired angle and maintained at that angle in aframework, e.g. of wire, but allows one side of a cloche to be fixed andthe other side to be hingeable for purposes of ventilation.

When moulding material for cloches, it is convenient to allow a fiatplain border of suitable size, say, one inch wide, around the edge ofeach sheet free from convexities, so as to enable the sheet to begripped or joined to neighbouring sheets.

Frames for cloches may be either of bent wire or of light channel or Tsection metal or plastic, and it is convenient with materials of suchlight weight as constitutes the cloche to provide anchoring means suchas serpentine pegs which may be driven into the ground.

It is possible to make structures, or even sheets of material accordingto the invention, out of two different materials having differentproperties. Thus, a cloche may be made with a top formed of onematerial, and the sides and ends formed of another material, thematerials being chosen for their resistance to ultraviolet light. Thetop may be chosen to be of a material more resistant to ultra-violetlight than the sides. During the day, when there is plenty ofultraviolet light falling at low angles of incidence, quite suflicientfor normal purposes may be obtained through the top, even though it issomewhat resistant to the ultra-violet light. The sides are arranged tobe of a material less resistant to the ultra-violet light,

and during the day they admit as much as can be accepted. During thenight, when the ground is radiating, the top of the cloche, beingsomewhat resistant to ultraviolet light, prevents its escape. Since theangle of incidence of rays radiated from the ground upon the sides ofthe cloche is very high, considerable internal reflection from the sideswithin the cloche will take place and therefore there will be less lossand more complete protection from frost.

ltwill be appreciated of course that under all circumstances the escapeof light or heat energy from the under side of a sheet of materialaccording to the invention will be considerably less than in the case oforthodox materials such as glass, since considerable diffusion andreflection of the heat will take place.

. I claim:

1. A greenhouse glazing comprising a sheet of imperforate translucentmaterial having a monoplanar body formed on only one side thereof with aplurality of concavo-convex bosses, each of said bosses being spacedfrom adjacent bosses by a distance at least equal to the width of one ofsaid bosses, and the thickness of the material being approximatelyconstant over the surface both of said body and of said bosses.

2. A greenhouse glazing comprising a sheet of imperforate translucentmaterial as in claim 1, said bosses being hemispherical.

3. A greenhouse glazing comprising a sheet of imperforate translucentmaterial having a monoplanar body formed on one side thereof with aplurality oi hemispherical concavo-convex bosses arranged in rows andspaced apart at distances of two diameters, center to center.

4. A greenhouse glazing comprising a sheet of imperforate translucentmaterial having a monoplanar body formed on one side thereof with aplurality of hemispherical concavo-convex bosses, each of said bossesbeing spaced from adjacent bosses by a distance at least equal to thewidth of one of said bosses, the thickness of the material beingapproximately constant over the surface of said body and over themargins of said bosses, and the thickness of the central portions ofsaid bosses being slightly greater than said constant thickness, wherebylenticular port-ions transmitting light rays are provided at the centersof and integral with said bosses.

References Cited in the file of this patent UNITED STATES PATENTS145,191 Hyatt Dec. 2, 1873 349,285 Pfeil Sept. 14, 1886 458,854 MarkSept. 1, 1891 586,249 Soper July 13, 1897 922,964 Schwickart May 25,1909 1,044,442 Carter Nov. 12, 1912 1,254,520 Macduff Jan. 22, 19181,263,065 Johanson Apr. 16, 1918 2,022,078 Dorey Nov. 26, 1935 2,084,599Sauer June 22, 1937 2,432,928 Palmquist Dec. 16, 1947 2,790,400Wasserman Apr. 30, 1957 FOREIGN PATENTS 44,011 France July 27, 1912795,978 France Jan. 13, 1936 408,686 Italy Jan. 5, 1945 450,065 ItalyJuly 7, 1949

